Nitric oxide (NO) has several functions of particular importance to human health [1,2]. It is now recognized as a key signaling molecule in the cardiovascular system [3]. NO has a central role in diverse pathological conditions, such as hypertension, ischemic heart disease, and stroke. There is an increased effort today aimed at the development of therapeutic and diagnostic products based on the new knowledge on NO. The importance of this field was highlighted with the 1998 Nobel Prize in medicine and physiology for their NO related research.
Despite significant scientific contributions in the field NO fluorescence detection [3-5], the development of novel dyes that are ratiometric and address some significant concerns with prior systems will not only provide practical alternatives for detection of this all important molecule in human physiology but also provide answers to fundamental questions about basic physiological functions of NO, which still remain. Over the last decade, NO-dependent signaling in the cardiovascular system has been modeled [6-9]; controversies regarding the role of NO in the vasculature have been reviewed [10]; as has reactivity of NO with biologically important thiols [11]. This work highlights the need for radically improved ways to assess one of the most important molecules for human physiology. Regretfully, quantification of NO in tissues remains a challenge due to the absence of a detection method that can combine significant spatial and temporal resolution with high NO specificity [12]. Indeed the current art for NO detection, which is the DAF-FM dye is non-ratiometric, has several shortcomings, and its reactivity with NO has recently become the subject of controversy [13]. These problems with existing technology for NO detection have led to intense efforts worldwide for developing new dyes for NO detection that operate by different mechanisms [4, 14-16].